Micro-machined mechanical and electromechanical devices are used in a wide variety of applications. For example, known applications of such structures include ink ejecting devices on printheads and some gimbals used to mount the record/playback head in the actuator arm of a hard disk drive. A wide variety of other applications for such devices are also either currently available or will likely become available in the near future.
The typical micro-machined mechanical device is constructed of one or more very small components fabricated from a single-crystal silicon substrate, or the like. Such substrates are well known for use in the manufacture of semiconductors, where they are usually formed into substantially circular disks that are commonly known as silicon wafers.
Silicon substrates such as wafers are particularly well adapted for use in flexible, micro-machined mechanical and electromechanical devices. Such substrates have a Young's modulus similar to that of steel, and when formed into the thickness of a traditional silicon wafer, they also are flexible and resilient. Moreover, the semiconductor industry's manufacturing equipment can be readily adapted to mass-produce such devices at low cost. Accordingly, literally thousands of micro-machined components can be manufactured using a single wafer.
Two critical elements of effective micromechanical component construction are 1) ensuring that the flexibility of the substrate is within acceptable limits; and 2) ensuring that the manufacturing techniques, such as precise etching at defined locations on the substrate, have been properly performed. Components manufactured with either of these critical elements missing or out of tolerance will not likely operate effectively.
Silicon wafer flexibility testing devices are available. For example, rotors and stators have been spaced apart from each other, bonded to a wafer, and operably connected to an electrical system such that the rotors and stators operate like a magnetic actuator when power is applied to the rotors and stators. The amount of voltage required to move the rotors and stators toward each other is proportional to the flexibility of the wafer. Accordingly, the flexibility of that particular wafer can be determined based on the determining the amount of voltage required to move the rotors and stators together.
While such devices allow the flexibility of that particular wafer to be determined, the physical bonding of the stators and rotors to the silicon wafer is time consuming and generally destroys a large portion of the silicon wafer. Accordingly, it is economically unfeasible to bond these devices to every wafer used to manufacture micro-mechanical components. Therefore, only a few wafers from a batch of wafers are usually tested. The remaining wafers in the batch are simply assumed to have the flexibility characteristics of the tested wafers from that batch.
In practice, the process of making wafers can lead to discrepancies in the flexibility of individual wafers in a given batch. Such individual discrepancies would not likely be caught using bonded test devices as described. Moreover, the bonded test devices are limited to only providing flexibility information about the wafer they are attached to. Bonded test devices do not assist with determining whether manufacturing tolerances have been maintained on a given silicon wafer.